It depends what is your requirements are like! If your threshold values are varying with time, create a lookup / using eval statement find the exact threshold value for that Hour. I will give an example
eval threshold=case(date_hour =9 threshold, "3", date_hour =11, "5")|eval State=case(value <= threshold, "Normal", value >= threshold*1.2, "warning", value >= threshold*1.5, "Critical")|Table State
then as i mentioned above replace the codes and place a image with relevant color to appserver/static/images folder. it will do the job what you want
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